Coloration of cotton fabric using watermelon extract: mechanism of dye-fiber bonding and chromophore absorption

Abstract

Different approaches have been taken to develop a greener and sustainable cotton coloration process to reduce carbon footprint. Natural compound as a colorant is an excellent alternative to the harsh chemical-based reactive cotton coloration process. However, natural coloration requires improvement in colorimetric properties and a better understanding of the colorant absorption mechanism. Here, we report a process for cotton coloration using bio-friendly natural colorant extracted from watermelon rind. The optical and colorimetric properties of watermelon rind saps (WRS) and WRS dyed cotton fabrics, dye-fiber bonding, chromophores absorption and color-fastness were studied. The experiment showed that the absorption of chromophores into the fabric mainly depends on their molecular weight, the position of the anchoring group and thermal stability. Chromophore adsorptions ranged from 55.4 to 81.7% resulting in excellent dye-fiber chemical potential. Coloration temperature and mordant significantly affect the colorimetric properties of cotton fabric as found in this study. All the dyed cotton samples showed good color-fastness to washing, water, rubbing, and perspiration. Furthermore, cotton dyed with WRS had better UV-protection factor (UPF) than that of the mosty used chemical-intensive reactive dyed sample. Finally, the ecological and economic aspects of WRS dyeing were also compared with commercial reactive dyes.

Keywords:

• Watermelon rind
• chromophore absorption
• chromophore molecular geometry
• UV protective cotton

Acknowledgements

Authors would like to highly acknowledge Mr. Shohag Sarkar, Mr. Bappi Sarker and Md. Mahmodul Hasan from South East Textiles Pvt. Limited, Bangladesh for supplying all fabrics and assisting in shade matching of natural and synthetic dyed samples. Authors also acknowledge the Department of Chemistry, Mawlana Bhashani Science and Technology University and the Centre for Advanced Research in Sciences (CARS), University of Dhaka, Bangladesh for providing FTIR and UV spectroscopy. Special thanks to the Central Laboratory of Public Health Engineering Department, Mohakhali, Dhaka, Bangladesh for characterizing the waste-water.

Disclosure statement

No potential conflict of interest was reported by the author(s).